As a therapeutic method for a stenosed site occurring due to plaque, a thrombus, or the like in a coronary artery, it is possible to utilize percutaneous transluminal coronary angioplasty (PTCA) (in which a blood vessel is caused to expand by using a balloon), a method in which a ramified or coiled stent indwells in a blood vessel as a support for the blood vessel, and the like. However, it is difficult to apply the above-referenced methods when plaque in a stenosed site is calcified and hardened or when a stenosed site occurs in a bifurcated portion of a coronary artery. Even in such a case (i.e., when plaque in a stenosed site is calcified and hardened or in a bifurcated portion of a coronary artery), atherectomy is a therapeutic method for incising a stenotic substance such as plaque, a thrombus, and the like that can be performed.
Japanese Patent Application Publication No. JP-T-2003-504090 discloses a device for atherectomy in which diamond particles (polishing materials) adhere to an outer surface of a rotary body in the tip portion (i.e., distal-most end) of a catheter. A stenotic substance is incised (i.e., cut out or removed) by rotating the rotary body inside a coronary artery. The rotary body of the device includes four bars arranged in a circumferential direction. When the bars are flexed to protrude radially outward, the rotary body can expand so as to fit a vascular diameter. This atherectomy device includes a linear motion shaft, which is movable relative to a tubular drive shaft in an axial direction in order to cause the bars to expand, inside the drive shaft which transmits drive force to the bars performing incision.